Submarine signaling



Oct. 23, 1928.

J. J. GILBERT SUBMARINE SIGNALING Filed June 1, 1926 Patented @da 23y @28 UNITE@ Sli't garant j carica.

TOEN J. GILBERT, 0F :PORT WASHINGTON, NEVI OEK7 ASSGNOR TO WESTERN ELEC- TIR-IG COMPANY, INCORPORATED, OF NEW YORK', lil'. Y., A CORPORATON OF NEW YORK.

SUBMABINE SGNALNG.

Application filed June 1,

rlhis invention relates to submarine signaling and particularly to terminal sections for loaded submarine cables.

An object of the invention is to reduce the disturbing eifect due to extraneous electric waves picked up by the cable.

I have hitherto proposed to decrease the interfering effect on received signals of extraneous electric waves picked up by a cable by providing an auxiliary loaded cable similar to the main cable and extending from the terminal apparatus to a location at sea about 500 ft. in depth. At the end of this auxiliary cable the core is connected to a metallic cap making contact with the sea water and near this sea-earth connection. a length of high resistance conductor is spliced into the core. This section of high resistance conductor is made equal in resistance to the characteristic impedance of the main loaded cable. which7 when the cable is suitably loaded, is practically a pure resistance at the frequencies of importance in cable work. In the terminal arrangement at the New York end of the permalloy loaded cable recently laid between New York and the Azores, this type of seaearth connection and terminating impedance are used.

In accordance with a preferred embodiment of the present invention a twin core cable sectione the cores of which have electrical characteristics differing from that of the loaded core of the main cable, is joined to the main cable and a terminating impedance grounded at sea. This terminal cable section extends to such a depth at sea that the amplitude of electrical disturbances originating near the surface of the sea and reaching the cable is small as compared to the amplitude of the signal current at this point. The terminal section should also extend to a point at sea. beyond which disturbances originating7 under the surface, such as that caused by nearby parallel cables, is negligible. .lt is preferable to employ terminal sections in which the two cores have similar electrical characteristics but some advantages may be derived even when employing a terminal section in which the cores have dissimilar electrical characteristics.

The invention may be more clearly understood by referring to the accompanying drawing in which Figl shows a twin core non-loaded terminal section connected to a i926. Serial No. 112,840

main cable and a terminating impedance at one end and to cable terminal apparatus at the other, and 2 shows a portion of a twin core terminal section in which the degree of leading is diminished progressively from the main cable to the terminal apparatus.

ln the drawing the main cable 2O comprises the conducting core 5, a wrapping of loading material 6 and an insulating material 7, suoli as gutta percha, in which the loaded conducting core is embedded. rll`he loading material 6 be of any material having suitable magn eticv properties as, for instancea a nickel-iron alloy containing 7 81/200 nickel and 2li/2% iron7 which is produced in accordance with the process described in patent to G. VJ .lflmen7 1,586,887, issued J une l.l926. rlhis alloy has the advantage of having a permeability 20 or 30 times that of iron at magnetizing forces'of the order of (L01 to 0.1() gauss and it has been found that the characteristic impedance of a cable loaded with such a material has a negligible reactance component at frequencies of interest inconnection with submarine cable signaling systems. rl`he metallic protecting sheath 22 is positioned about the insulating material 'l' and. a material 2l, pervious to water, is wrapped about the sheath 22. Y

rlhe terminal cable secticn comprises the twin core conductors 9 and l0 surrounded by the insulating material 8, these conductors having electrical characteristics different from the electrical characteristics of the main cable. llhe conductors 9 and l0 as shown in Fig. l are non-loaded but these conductors may, in another aspect of this invention, be loaded in a different degree from that of the main cable. For instance, the loading may he tapered so that the degree of loading is progressively diminished from the main cable to the receiving apparatus. in this case, the electrical constants of corresponding small sections of the two conductors are preferably equal. In Fig. 2 is shown a portion of a twin core terminal section in which the conductors 27 and 28 are loaded to a dilfcrent degree at different portions of the cable respectively, by means of the loading material 29 and 30, Referring again to Fi l, one end of the conductor 9 is connected to the core 5 of loaded cable 2O and the other end is con ne'cted to the 'terminal apparatus. Conductor l() connects, at one end, to the terminal `apvto a negligible value.

paratus and is grounded at the other end to the metallic protect-ing sheath 12. The protecting sheath 12 and the pervious material 13 are similar to and preferably continuous with the sheath 22 and the pervious material 21 respectively of the loaded cable 20. The terminating impedance 14 is spliced into conductor 10 near its grounded end. As stated above, the characteristic impedance ot a loaded cable is nearly a pure resistance, the value of which may be lcalculated trom the inductance L and the capacity C of the cable by the formula R: 1/ L/ C. A preferred form of terminating impedance consists of a suitable length of high resistance stranded wire, such as nichrome, having a total resistance substantially equal to the characteristic impedance of the loaded cable, that is, the portion of the cable seaward from the seaearth connection. This artificial line is preterably spliced into the cable conductor by soldering the individual strands of resistance wire to one or more strands of the cable conductor.

The terminal apparatus is oli the usual type used in cable systems employing duplex operation and consists essentially of the transmitting apparatus 15,- receiving apparatus 16, the condenser-s 17 and 18 of equal capacity and the grounded networks 25 and 2G which are employed to correct for unbalances between the signaling conductor and the seaearth conductor. A system employing such networks is described in detail in U. S. patent to O. E. Buckley, No. 1,567 ,316, December 29, 1925.

We have then a terminal section for a loaded cable in which the conductors 9 and 10 are connected, at one end, to the receiving apparatus 16. At the other end, conductor 9 is connected to the loaded cable 20 and conductor 10 to the grounded terminating impedance 14. This terminal section extends from the terminal apparatus to a location at which the sea is substantially 500 ft. deep.

At such a depth the electrical disturbances originating at the surface of the sea cause a negligible disturbing current to ilow in the cable. The terminal section should, furthermore, extend to a location which is at a considerable 'distance from submarine disturbances as, for example, other cables, so thatthe eEect of these disturbances will be reduced Electrical disturbances picked up at any point along the terminal section will cause equal volta-ges to be induced in each of the conducting cores 9 and 10. Where the cores are similar throughout and their terminating impedances, i. e., the impedances of the loaded main cable and the artificial line, are equal, the magnitude of the disturbing currents in each core will be equal at any position on the terminal cable section. Under these conditions, the disturbmg currents reaching the receiving apparatus will be equal in inagniture but opposite in phase and will therefore annul each other.

Vhile the impedance of the terminating impedance is preferably made equal to the impedance of the cable seaward from the seaearth connection and while the cores 0f the terminal section are preferably similar electrically, yet, where these conditions are not found, disturbing currents due to reflected waves may be prevented by maintaining a correct relation between the impedance values oi these elements. This relation should be such that the ratio of the characteristic impedance o' the conductor 9 to that of conductor 10 is equal to the ratio of the characteristic impedance of the main cable 2O to that ot the terminating impedance 14, that is, where Z9, Zlo, Z5, and ZH, represent respectively, the characteristic impedances of the conductors 9 and 10, the cable 5 and the terminating impedance 14,

The improved terminal cable section for loaded cables has been shown and described in connection with one form oi' duplex terminal apparatus. It is adapted, however, for simplex as well as duplex systems and for other terminal arrangements of duplex apparatus than that shown. For example, the invention may be employed in such systems as those disclosed in U. S. patent of II. S. Osborne, No. 1,390,580, September 13, 1921. It has an additional advantage when used in duplex systems over simplex systems, in that the ditlicult problem of providing a balancing network for balancing the head end of the cable for duplex operation is simplified.

What is claimed is:

1. In a submarine signaling system, a loaded cable, receiving apparatus and a sea-earth connection for said cable, and a twin core terminal section connecting said cable to said sea-earth connection through said receiving apparatus, said terminal section having a distributed inductance different from said cable.

2. In a submarine signaling system, a loaded cable, receiving apparatus and a sea-earth connection for said cable, said sea-earth connection Vbeing located at a sea depth of substantially 500 Jfeet, and a non-loaded twin core terminal section connecting said loaded cable to said sea-earth connection through said receiving apparatus.

3. In a submarine signaling system, a loaded cable, terminal apparatus therefor, a terminating impedance, a non-loaded twin core terminal section connecting said terminal apparatus with said loaded' cable and said terminating impedance, and a sea-earth connection for terminating said terminating impedance.

4. In a submarine signaling system, a loadfil ed cable, terminal apparatus therefor, a terminating impedance, a non-loaded twin core terminal section connecting said terminal apparatus with said loaded cable and said terminating impedance, and a sea-earth connection, located at the seaward end of said terminating impedance and at a sea depth of substantially 500 feet, for terminating said terminating impedance.

5. In a submarine signaling system, a load ed cable, a terminating impedance for simulating the impedance of said cable and located at sea at such a depth that the cable located farther out at sea will be substantially free from the influence of external disturbances, a receiving circuit for receiving messages transmitted over said cable, and two similar conductors connected to said receiving circuit, one extending to said terminatingimpedance and the other to said cable at a point corresponding in location to that of said terminating impedance, said similar conductors having impedance characteristics different from said loaded cable.

6. In a submarine signaling system, a cable, a two conductor terminal section therefor, the conductors in which have impedance characteristics different from said cable, a terminating impedance, the two conductors of said terminal section being connected to said cable and to said terminating impedance respectively, and the ratio of the impedance of said cable to that of said terminating impedance being substantially equal to the ratio of the impedance of the terminal conductor connecting to the cable to the impedance of the terminal conductor connecting to said terminating impedance.

y 7 The method of diminishing the interfering effect of extraneous electric waves picked up by a loaded submarine cable employing a non-loaded twin core terminal section and a sea-earth connection, which comprises immersing said sea-earth connection in a depth of water of substantially 500 feet and extending said twin core terminal section to said seaearth connection.

8. In a submarine signaling system, a loaded cable, receiving apparatus and a sea-earth connection for said cable, and a twin, core terminal section connecting said loaded cable to said sea-earth connection through the receiving apparatus, the electrical characteristics of said twin cores being different from the electrical characteristicsof said loaded cable.

In witness whereof, I hereunto subscribe my name this28th day of May A. D., 1926.

JOHN J. GILBERT. 

